1. Field of the Invention
The present invention relates to a solid-state image capturing device, a method of manufacturing such a solid-state image capturing device, a method of designing such a solid-state image capturing device, and an electronic device, and more particularly to a solid-state image capturing device having color filters of R (red), G (green), and B (blue), a method of manufacturing such a solid-state image capturing device, a method of designing such a solid-state image capturing device, and an electronic device.
2. Description of the Related Art
Electronic devices such as electronic digital video devices and electronic digital still devices have a solid-state image capturing device which may include a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal-Oxide-Silicon Transistor) image sensor, or the like.
The solid-state image capturing device includes a matrix of pixels arrayed in horizontal and vertical directions on a semiconductor substrate, providing a photosensitive surface. Each of the pixels on the photosensitive surface has a sensor including a photoelectric converter such as a photodiode, for example.
The solid-state image capturing device also includes a light condensing structure disposed above the photosensitive surface for condensing the light of a subject image onto the sensors of the pixels. The sensors detect the condensed light of the subject image and photoelectrically converts the detected light into signal charges, generating a pixel signal.
With the CCD image sensors and CMOS image sensors according to the related art, the photodiodes photoelectrically convert the light applied to the sensors into signal charges to be output as an image signal. Specifically, the CCD image sensors and CMOS image sensors convert the light that is applied to the sensors during a certain exposure time into signal charges and store the signal charges.
Since the amount of signal charges that can be stored is limited, when intensive light is applied to the sensors, they tend to be saturated making white and black gradation levels insufficient. Stated otherwise, though the solid-state image capturing device has a certain range of incident light intensity levels for producing appropriate output signals, the range of incident light intensity levels is very small compared with the range of light intensity levels emitted from the subject to be imaged.
There have been demands in the art for technologies for expanding the dynamic range of solid-state image capturing devices.
Some technologies that have been proposed in the art for expanding the dynamic range of solid-state image capturing devices will be described below. M. F. Snoeij, et. al., “A Low-Power Column-Parallel 12-bit ADC or CMOS imagers,” 2005 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors, pp. 169 and T. Otaka, et. al., “12-Bit Column-parallel ADC with Accelerated Ramp,” 2005 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors, pp. 173 discloses a technology for changing intervals at which applied light is photoelectrically converted depending on the intensity of the applied light. Japanese Patent Laid-open No. 2008-167004 discloses a technology for setting a gain depending on the intensity of applied light.
Japanese Patent Laid-open No. 2006-333439 discloses a solid-state image capturing device including light-shielding members for shielding photoelectric converters from light and actuators, constructed according to the MEMS (MicroElectroMechanical System) technology, for actuating the light-shielding members.
There has also been proposed a material-based approach to expand the dynamic range of solid-state image capturing devices, instead of the above device-oriented technologies for expanding the dynamic range of solid-state image capturing devices.
Japanese Patent Laid-open Nos. Hei 1-248542 and Hei 10-65129 disclose a process for expanding the dynamic range of a solid-state image capturing device by modulating light with either a material applied to a glass surface of the casing of the solid-state image capturing device or a material disposed between the glass surface and the solid-state image capturing device.
Japanese Patent Laid-open No. Hei 1-236649 discloses a process for expanding the dynamic range of a solid-state image capturing device by modulating light with a material grown as a film in front of the sensors.
Japanese Patent Laid-open No. Hei 4-65163 discloses a process for applying a photochromic material to a surface outside of photodiodes.
Problems that cannot be solved by the above disclosed technologies according to the related art include a time shift that occurs when a moving image is captured or when images are captured in succession. Specifically, solid-state image capturing devices of the readout type suffer a time shift at the time image data are read out a plurality of times and also at the time longer and shorter electric charges are stored, and solid-state image capturing devices incorporating a mechanical shutter suffer a position-depending time shift. Accordingly, images captured by those solid-state image capturing devices are not completely free of some oddities.
The material-based technologies described above have been difficult to incorporate into solid-state image capturing devices because specifications that are determined by the signal processing speed of the solid-state image capturing devices are not satisfied by the response speed of photochromism.